There’s mounting evidence that maintaining a healthy ecosystem of gut bacteria in our microbiome can have a wide range of health benefits. And there are many things we can do (and eat) to help create and maintain a favorable composition of gut bacteria.
But, how do our microbiomes get out of whack in the first place?
6 Factors that Can Upset Bacterial Balance in the Gut
Unfortunately, many factors in our modern world can have the side effect of harming the probiotic bacteria that we have in our guts and upset the delicate balance of healthy bacteria that is optimal for our health. Upsetting the microbial balance in our digestive systems can have negative effects on our digestive system, nervous system, metabolic system and immunological system.
In utero, babies have a “clean” digestive system without any bacteria, but they receive their primary bacterial exposure from their mothers, first as they pass through the birth canal and later as they drink breast milk, rich in their mother’s healthy bacteria. In this way, bacteria can be “inherited” from one generation to the next and may have even co-evolved with humans over the years.
Since babies receive their first exposure to healthy bacteria from their mothers, via the trip down the birth canal and from drinking breast milk, being born by Cesarean Section or being fed by formula can affect which bacteria the baby is exposed to and which bacteria colonize the baby’s gut.
It has been shown that babies born by C. Section have reduced bacterial diversity and lower levels of good bacteria than those that are found in babies delivered via the birth canal. In fact, the microbiome in the vagina changes dramatically during the course of pregnancy. Pregnant women’s vaginas contain high levels of Lactobacillus johnsonii, which is normally found only in the gut and assists in the digestion of milk. This change in the mix of bacteria during pregnancy may be another way where the mother’s body nurtures her newborn baby, preparing him to digest the milk that will soon become his diet.
Researchers Dr. Anders Andersson, of KTH Royal Institute of Technology and Science for Life Laboratory in Stockholm, and Dr. Maria Jenmalm, of Linköping University have proposed additional studies to determine whether it could be beneficial to babies delivered via C. section to transfer bacteria from their mother’s vaginal flora to them or to give them probiotic supplements. There are many good reasons to deliver a baby by Cesarean Section, primarily to preserve the health of the mother and baby, but as research about the importance of the microbiome evolves, standard pediatric medical recommendations may start to include exposing the infant to the bacteria found in their mother’s vaginal cavity or providing a probiotic soon after birth, to promote healthy bacterial colonization and development of the immune system. It is not far-fetched to imagine procedures evolving to smear vaginal bacteria onto a baby delivered by C. Section, and this may already be happening, although I’ve not yet heard of this (please comment below if you have).
Feeding of Infants
Babies fed by formula have a different mix of gut bacteria than do babies fed by breast milk. Scientists at Duke University have found that the healthy bacteria, which aid in nutrient absorption and immune system development, that colonized the guts of babies fed breast milk did not colonize the guts of those fed infant formula. Recently, medical researchers have determined that a mother’s gut bacteria actually get into her breast milk and then colonize her baby’s digestive tract, aiding in nutrient absorption and immune system development.
Researchers at the University of Illinois (Dr. Hannah D. Holscher and her colleagues) examined the immune system development and the gut bacteria colonization of formula fed babies. One group in the study was given prebiotics and probiotics enriched formula and the control group was given standard infant formula only. The study showed that the group given probiotic enriched formula had significantly increased development of disease-resisting intestinal bacteria, showing that what a baby is fed in infancy impacts the colonization of his gut-by-gut bacteria.
After more research is done, it may be that the standard medical recommendations for infants fed by formula soon after birth will include probiotic supplementation.
Without the invention of antibiotics, our population would be significantly smaller than it is today. I, myself, could have died several without antibiotics. After my placenta did not deliver spontaneously following the birth of my son and my doctor had to insert her hand into my uterus to dislodge it – the procedure introduced dangerous bacteria into my body. I developed bacterial pneumonia that was treated successfully by antibiotics three times in my life, soon after birth, in elementary school and a few years ago.
However, antibiotics are a major source of disruption of our balance of our gut bacteria. When administered to stop a dangerous bacterial infection, antibiotics can be lifesaving, but this benefit is not without cost. Their whole purpose is to kill bacteria and they do not distinguish between good and bad bacteria. It has been shown that the mix of gut bacteria of patients can remain disrupted from their pre-treatment levels for up to four years following antibiotic treatment.
When large numbers of good bacteria are killed by antibiotics, space and food become available for other bacteria, who were not as affected by the antibiotics (such as antibiotic resistant bacteria and fungi, such as yeasts (e.g. candida)), to increase their numbers in the gut and prevent the regrowth of the healthy gut bugs. Infections caused by the antibiotic resistant bacterium, Clostridium difficile (C. difficile) are common following a bout of antibiotics and can be quite difficult to eradicate. This is often the cause of diarrhea which is known to be a side effect of antibiotics.
Babies are particularly susceptible to the effects of antibiotics on their gut bacteria. Their gut microbiome is still being established during the first two months of life. Taking antibiotics early on can disrupt the healthy colonization of their digestive tract by healthy bacteria.
In addition to concerns about antibiotic resistance (a form of drug resistance whereby the antibiotic loses its ability to kill the bacteria), the devastating effect antibiotics can have on our microbiome is added reason to take antibiotics infrequently and only when truly necessary. The medical community has evolved to become much less likely to prescribe antibiotics for a runny nose (or even a virus!) than it was twenty years ago. Some doctors now routinely recommend that their patients who have been prescribed antibiotics also take a probiotic during and after the course of treatment.
By now, we all know that stress is unhealthy. It raises blood pressure, affects the immune system, disrupts sleep, causes head aches and can even raise blood cholesterol levels. I was surprised to learn, however, that human stress is also unhealthy for our gut microbiome.
Dr. Michael Bailey and his colleagues at the University of Ohio examined the gut bacteria of mice. They then subjected the mice to stress causing stimuli and again examined the composition of gut bacteria. For those mice subjected to the stress, there was a significant change in the composition of their gut bacteria. There were fewer healthy bacteria (Bacteroides) and greater numbers of unhealthy ones (Clostridium). Dr. Bailey has said of this research, “These bacteria affect immune function, and may help explain why stress dysregulates the immune response.” He is saying that his research might explain why we are more likely to get sick following bouts of stress.
When I was in school, almost without fail I would fall ill as soon as my final exams were over. This may also explain why giving rats with stress related intestinal disorders (such as irritable bowel syndrome), probiotics seemed to improve the rats’ conditions. Scientists at the University of Michigan have determined that not only does stress change the bacterial colonization of the gut, but also that this change in bacteria in the gut actually causes inflammation of the intestines. The researchers concluded that this may be why probiotics seem to help patients with stress induced gastrointestinal disorders.
Although probiotics may be helpful to maintain gut health in stressed individuals, trying to manage or control stress is even better, given that stress negatively affects multiple parts of the body, not just the digestive system. Keep up the exercise, yoga, meditation and healthy eating and make time for hobbies and hanging out with friends!
Drinking alcoholic beverages excessively can reduce the number of healthy bacteria in your digestive tract.
In a study that could never be done in the US for ethical reasons, Russian researchers studied the gut bacteria composition of men admitted to a psychiatric hospital due to alcoholic psychosis and compared them to a control study of men who did not drink alcohol. At the start of the study, the alcoholic drinkers had significantly reduced numbers of beneficial bacteria (bifidobacteria, lactobacilli, and enterococci) in their digestive tract than did the non-drinkers. The heavy alcohol drinkers also had elevated liver enzymes, showing liver damage.
The men were then randomly assorted into groups, one to receive the standard therapy of abstinence plus vitamins and the other to receive probiotics (Bifidobacterium bifidum and Lactobacillus plantarum). After 5 days of treatment, the group that received the probiotics had significantly restored healthy gut bacteria as opposed to the standard therapy group. Interestingly enough, the liver enzymes that were markers of liver disease went down for the group that received the probiotics. This is very exciting and I look forward to more studies that will examine the effect of probiotics on liver disease.
Dr. Scott Gabbard and his colleagues at Dartmouth-Hitchcock Medical School have determined that even moderate drinking can cause small intestinal bacterial overgrowth (SIBO), which can cause diarrhea, abdominal discomfort, weight loss and nutritional deficiencies. Typically, most bacteria are found in the large, not the small intestine, and when they grow in large numbers in the small intestine it creates problems for the patient with SIBO. The study showed that even moderate drinkers had a significantly elevated risk of SIBO as compared to those patients who did not drink.
Fortunately, the news is not all bad for wine drinkers. A small Spanish study found that men who drank one glass (a generous 9 ounce pour!) of red wine daily for the duration of the study, as compared to the controls groups, one of which abstained from alcohol and the other of which had one gin drink daily, had higher levels of certain beneficial bacteria in their guts than did the other control groups. The researchers concluded that small amounts of red wine are beneficial for the gut microbiome.
I hope that further research will conclude that the benefits from a daily glass of red wine outweigh the risk of SIBO. Until I hear otherwise, I’ll keep up my red wine habit!
There is a well documented relationship between which types of gut microbes you have and a tendency towards either obesity or thinness. Studies have shown that using fecal transplants to change the mix of microbes can cause weight loss or weight gain, depending on which bacteria are introduced.
We are now finding out that ingesting artificial sweeteners alters the composition of microbes in the digestive tracts of those people who regularly use them. Unfortunately, the types of microbes that tend to thrive with a diet of Saccharine and other non-sugar sweeteners are those microbes that are very good at helping our digestive system to 1.) harvest calories from the food that is eater, and 2). signalling to the body to store the calories as fat (rather than expending them as energy).
This means that by using artificial sweeteners in an attempt to save calories and lose weight, you are actually altering your gut microbiome in a way that promotes weight gain. “In other words, artificial sweeteners may favor the growth of bacteria that make more calories available to us, calories that can then find their way to our hips, thighs and midriffs,” says Peter Turnbaugh of the University of California, San Francisco, an expert on the interplay of bacteria and metabolism.
This is one example of how chemicals used in our food affect the gut microbiome in unexpected and sometimes unwanted ways.
The following articles provide additional information on the topics discussed here:
- Here & Now on National Public Radio (September 10, 2013). Research Shows that Microbes are Crucial for our Health.
- The New York Times (June 18, 2012). Tending the Bodies’ Microbial Garden.
- Science Daily (March 22, 2011). Stress affects the balance of bacteria in the gut and immune response.
- Science Daily (August 22, 2013) Breast is Best: Good Bacteria Arrive from Mom’s Gut via Breast Milk.
- Science Daily (November 28, 2011) Moderate Alcohol Consumption is Associated with Small Intestinal Bacterial Overgrowth, Study Finds.